Shock sensors employing reed switches am used in motor vehicles to detect a vehicle collision. When a collision occurs, the shock sensor triggers an electrical circuit for the actuation of safety devices such as inflating air bags, tensioning seat belts, and other similar systems. Such shock sensors typically employ a reed switch with an acceleration sensing magnet which is biased by a spring away from an activation region of the reed switch such that the reed switch is open when the shock sensor is not subject to acceleration.
When the vehicle and the shock sensor, which is attached to the vehicle, are subject to a crash-induced acceleration, the magnet acts as an acceleration-sensing mass. The magnet moves relative to the central activation region and exposes the reeds of the switch to a magnetic field, which causes the reeds to mutually attract and close the reed switch. I have disclosed in my earlier patent, U.S. Pat. No. 5,194,706, a shock sensor employing end-actuation in a compact package. My previously disclosed shock sensor achieves considerable advantages in reduced package size which facilitates placement of the shock sensor within the automobile. Placement of shock sensors may be critical to reliable and effective operation since smaller sensors may be readily placed in effective locations. My previous sensor achieved improved minimum dwell times through the shaping of the magnet and the employment of the end-actuation region of a reed switch. Reed switches, as typically manufactured, have a fairly wide range in magnetic field strength (measured in amp turns) required for their actuation. Thus, manufactured reed switches are normally tested and sorted according to field strength requirements for actuation. A certain number of reed switches must be discarded if outside the usable range for a particular shock sensor construction.
As crash actuated safety devices become standard in more cars and trucks, shock sensors are increasingly in demand. Features which can reduce costs in manufacturing are especially desireable. Particularly, a shock sensor is needed which has a reduced part count which is adaptable to machine assembly and which may be readily adapted to accommodate the unique tolerancing variation associated with reed switches.